Cornellians looking to wish upon shooting stars can catch sight of the upcoming annual meteor showers — the Lyrids will peak before dawn on April 21 and 22, and the eta Aquariids will descend upon the sky at its peak May 4 and 5.
Each meteor shower is named after the point in the sky that the meteors appear to be coming from — the Lyrids radiate out from the constellation Lyra, while the eta Aquariids appear to come from the constellation Aquarius.
These bright streaks that illuminate the sky have captured humans’ wonder for millennia, as dashes of light race across the sky during spectacular shows called meteor showers.
Although a grandiose sight, meteor showers come from small pieces of rock burning in the atmosphere.
Comets, which are cosmic ice balls of frozen rock and dust, travel in an elliptical orbit around the sun. As a comet orbits, the ice surrounding small particles of rock vaporizes, leaving behind the rock debris that continues to travel with the comet.
Due to pressure caused by radiation from the sun, the small pieces of rock deviate from the comet, creating a stream of debris around and behind it — forming the comet’s characteristic tail.
According to Prof. Philip Nicholson, astronomy, every year, the orbit of Comet Thatcher intersects or touches the Earth’s path around the sun. This crossing causes debris from the comet to enter the Earth’s atmosphere and burn, producing the streaks of light seen as “shooting stars” during the Lyrids meteor shower.
Relatively unchanging comet orbits guarantee annual meteor showers, while other meteor showers occur more sporadically, Nicholson said.
While most meteor showers originate from comets, a few can also come from asteroids. Defined by their lack of a characteristic comet tail, such asteroids are former comets that have lost their gases and ice because the sun evaporated them. However, the dusty rock debris that still surrounds the asteroid can diverge and cause a meteor shower, according to Nicholson.
Nicholson added that dust from an asteroid can be a centuries-old relic from its time as a comet.
“It may be that the dust making up the meteor shower actually came off [an asteroid] when it was still a functioning comet,” Nicholson said. “The dust may stay in orbit for centuries before entering the Earth’s atmosphere.”
Regardless of the origin of the meteor showers, the debris that burns up in the Earth’s atmosphere ultimately causes the appearance of bright streaks across the sky.
While the meteors seen from Earth appear to be large in the night sky, in reality, the debris is typically the size of a sand particle. Pieces of debris that are a few millimeters larger would produce a more explosive type of meteor called a fireball, Nicholson said.
Nicholson explained that as the meteor enters the atmosphere, a longer amount of time is required for the heat to reach the center of a larger-sized meteor. But since meteors only pass through the atmosphere for a few seconds, some meteors cannot withstand the rapid buildup of heat, leading to an explosion, Nicholson said.
“Some of them explosively disintegrate when they get to a certain amount of heat on the inside,” Nicholson said. “That’s what produces what looks like a visible explosion.”
Although an infrequent sighting, fireballs can appear in a select few meteor showers — including the Lyrids meteor shower peaking this week.
The frequency and duration of meteor showers and fireballs can also be inconsistent because the debris of each comet is not entirely uniform.
If more debris enters the Earth’s atmosphere, more meteors will streak through the night, meaning the number of meteors viewers can expect to see will fall within a predicted range, Nicholson said. The Lyrids is estimated to have around 10 to 15 meteors per hour.
Both of the spring meteor showers are expected to show a number of meteors in the northern hemisphere, with eta Aquariids anticipated to be one of the strongest showers this year. For those who plan to view these meteor showers, Nicholson advised students to visit a place with less light pollution, such as Mount Pleasant — a prime stargazing spot in nearby Dryden that is also home to Cornell’s Hartung-Boothroyd Observatory.
“You really need a dark, moonless night to watch for meteors,” Nicholson said. “[It’s] best to find a spot on a hilltop outside of Ithaca … or a dark corner of [the botanical gardens] if you don’t have a vehicle.”
Ngoc Truong grad, who works with Prof. Jonathan Lunine, astronomy, also advised students to check the weather for clear skies before camping out to see the meteor shower.
According to Truong, the meteor shower will likely be the most visible at around 2 a.m. or 3 a.m. on April 22.
The eta Aquariids might make a brighter showing, as Nicholson said the moon will only be 27 percent illuminated, creating a dark backdrop for the shining meteors.